Combination pulse jet and ram jet engine



May 4, 1954 w. COLLINS COMBINATION PULSE JET AND RAM JET ENGINE 2 Sheets-Sheet l Filed June 5, 1948 IMNNK INVENTOR. WHITNEY COLL/NS ATTORNEYS.

May 4, 1954 W. COLLINS COMBINATION PULSE JET AND RAM JET ENGINE Filed June 5, 1948 POU/VDS 0F FUEL PER POUND 0F T HRUST PER HUUR 2 Sheets-Sheet 2 T HRUS T S AHS/25g@ l RAM \ PULSE Y s2 I MA cH A/RSPEED IN V EN TOR. WH/ TNEY GOL L /lVS ATTORNEYS.

Patented May 4, 1954 UNITED QTNT OFFICE COlVmlNATIQN PULSE JET AND RAM JET ENGINE Application .lune 5, 1948, Serial No. 31,291

(Cl. SCL-35.6)

Claims.

This invention relates to jet engines, especially to the ram jet and pulse jet types.

A characteristic of ram jet engines is their inehciency at low velocities. To be at all practical, ram jet engines have to be operated in the sonic or supermscnic ranges. Pulse jets operate with reasonably good efficiency in the sonic range, but cannot compare in effectiveness with ram jets above sonic speeds.

It is an object of this invention to provide a combination pulse jet and ram jet engine in which the engine operates asa pulse jet until some speed in or near the sonic range is reached, whereupon the engine begins to operate as a ram jet.

This and other objects are accomplished in an elongated housing open at both ends, the for- Ward end of which may be held closed under certain conditions for operation as a pulse jet. When certain flight conditions obtain, the forward end opens up automatically and the engine operates as a ram jet.

In the drawings:

Fig. l is a longitudinal section of an engine made according to the invention, showing the housing in condition for operation as a pulse jet. Fig. 1A is an enlarged fragmentary diagrammatic view of a pressure actuated control switch device.

Fig. 2 is a View in section of the extreme forward end of the engine, showing the engine in condition for operation as a ram jet.

Fig. 3 is an enlarged detail View of the pulse jet valves shown in Fig. l, the valves being shown closed in Fig. 3.

4 is a View similar to Fig. 3, but showing the valves open. Y

Fig. 5 is a performance curve showing comparative spccic fuel consumption of ram and pulse jets plotted against air speed, and

Fig. 6 is a performance curve comparing the thrust of a pulse jet with that oi a ram jet, plotted against air speed.

The jet engine of this invention consists of a single housing in which is disposed a pulse jet engine and a ram jet engine. The housing consists of an elongated member 2 being open at both ends. A plug 4 is positioned to close the forward end. The plug l is movable axially of the housing 2 in an inner body 5, the latter being supported by any suitable means such as struts 8.

A motor it is mounted in the inner body and is connected to move the plug d from its closed position as seen in Fig. l to its open position as seen in Fig. 2. Motor l@ may be any suitable electric motor. but it will be found convenient to utilise the fuel pressure as a motivating force. To that end, motor lil may conveniently comprise a hydraulic cylinder in which a piston Illa is reciprocable to move the plug t. The piston will preferably be spring biased in one direction, and suitable connections will be ma-de from the fuel supply to the cylinder to move the piston against the spring bias.

Some suitable means will be provided to automatically activate the motor Ill. The control means may for example be responsive to air pressure or to speed, or possibly to both air pressure and speed. As an example, a primary relay consisting of a pressure actuated micro-switch i2 may be located in the nose of the engine. This location may be in the movable plug as shown in Fig. l. Pressure is communicated through passage IZa to diaphragm i213, a spring I 2c urging the switch contacts 52d apart against the resistance of the pressure on the diaphragm. A predetermined increase in pressure will close switch contacts |211. A secondary relay Il! isv connected by a suitable cable I to the primary relay IZ. The secondary relay M may be a sole-` noid operated valve in a pipe connecting the hydraulic cylinder with the fuel tank, the solenoid idc being energized on closing of the contacts 2d to move the valve Mb against the spring I fic to ope-n the fuel pressure line to the cylinder of motor I 0 to retract the piston Illa against the spring,

To provide for pulse jet operation, a plurality of valved air passages is provided in the housing somewhat back from the nose of the engine. rlhese valved passages consist of a plurality of openings I8 provided in the housing 2, button type valves 20 to close the openings i8, and a screen 22 to hold the buttons in position.

Housing 2 encloses a combustion chamber 2d positioned to receive air from the valved air passages. A plurality of flame stabilizers 293 of any suitable design Will serve to keep the ignited gas from blowing itself out. Fuel may be supplied in any suitable manner as by a fuel nozzle shown at 28. An igniter 3G may be provided to light the mixture at the beginning of operation.

Fig. 5 shows in a general Way how the speciiic fuel consumption of a ram jet engine compares with that of a pulse jet engine. The curve 32 shows the consumption for a ram jet engine, and the curve 3@- shows fuel consumption for a pulse jet engine. The point X is indicated as the point of intersection of the two curves. @om the standpoint of maximum fuel economy, the control system cf the motor would be set to open the front end of the engine tube at air speed S1.

It may be noted, however, that there might be other considerations. The curves shown in Fig. 6 illustrate the comparative thrusts of the two types of engine. The curve 3S illustrates the type of curve for a pulse jet engine, and the curve 38 illustrates the type of curve for a ram jet engine. These two curves are shown as intersecting at point Y, at air speed Sz. S1 and Se are not necessarily the same.

Operation In operation, the controls for motor l@ will be set to keep the plug 4 in the closed position as shown in Fig. l for the purpose of getting the engine airborne and until it reaches a given speed. With plug ll closing the forward end of the housing 2, the housing is in effect a pulse jet engine, with air entering the air passages in the housing according to the well-known cycle of pulse jet engines.

As soon as the engine vattains certain pre-determined flight conditions, the motor controls operate to activate or energize the motor to make it'move the plug l rearward to the position shown in Fig. 2, and to hold it in that position as long as the pre-determined light conditions obtain. The housing then begins to function as a ram jet engine, during which time the pressure in the housing will be suincient to keep the button valves 26 seated against the edges of the openings I8.

I claimt 1. In a power plant of the character describedy an elongated engine casing having an internal combustion chamber and air inlet openings and valve means for said openings operable in response to pressure variations in said combustion chamber to open and close said valve means and thereby make said power plant become operable as a pulse jet engine, an air inlet opening in the forward end of said casing, valve means for said opening and means actuating said sec ond mentioned valve means and operable to open said front end of said casing to the entrance of air to said combustion chamber and thereby make said power plant operable as a ram jet engine, said first mentioned valve means being closed by the substantially constant pressure developed in said combustion chamber under ram jet operation and means supplying fuel to said combustion chamber.

2. In a power plant of the character described, an elongated engine casing having an internal combustion chamber and air inlet openings and valve means for said openings operable in response to pressure variations in said combustion chamber to open and close said valve means and thereby make said power plant become operable as a pulse jet engine, an air inlet opening in the forward end of said casing, a valve means for said opening and means actuating said second mentioned valve means and operable to open said front end of said casing to the entrance of air to said cumbustion chamber and thereby make said power plant operable as a ram jet engine, said rst mentioned valve means being closed by the substantially constant pressure developed in said combustion chamber' under ram jet operation, and means supplying fuel to said combustion chamber, said means actuating said second mentioned valve means comprising control means therefor operable in response to a predetermined operation of said engine and to make said power plant inoperative as a pulse jet engine.

3. In a power plant of the character described, a housing consisting of an elongated tubular casing open at both ends and having a combustion chamber, a plug axially movably supported in said casing and operable to close or open the open front end of said casing, air inlet openings in said casing for admitting air to the combustion chamber, means injecting fuel into said combustion chamber, valve means for said air inlet openings and operable in response to pressure variations in the combustion chamber when said plug is moved to a position closing the front end opening of said casing for making the power plant operate as a pulse jet engine, and means actuating said plug to move same to a position opening the front end opening of said casing, and control means for said plug actuating means and operable in response to a predetermined operation of said power plant to actuate the aforesaid plug actuating means to open the front end opening of said casing and thereby make said power plant V`operable as a ram jet engine in which a substantially uniform high combustion pressure is continuously maintained in the combustion chamber suflicient to close said air inlet valve means and make said power plant incapable of operation as a pulse jet engine.

4. In a power plant of the character described, a housing consisting of an elongated tubular casing open at both ends and having a combustion chamber, a plug axially movably supported vin said casing and operable to close or open the open front end of said casing, air inlet openings in said casing for admitting air to the combustion chamber, means injecting fuel into said com bustion chamber, valve means for said air inlet openings and operable in response to pressure variations in the combustion chamber when said plug is moved to a position closing the front end opening of said casing for making the power plant operate as a pulse jet engine, and means actuating said plug to open or close the front end opening in said casing, said last mentioned means operable to make the power plant operate either as a pulse jet or a ram jet engine.

5. In a power plant of the character described, a housing consisting of an elongated tubular casing open at both ends and having a combustion chamber, a plug axially movably supported inA said casing and operable to close or open the open front end of said casing, air inlet openings in said casing for admitting air to the combustion chamber, means injecting fuel into said cornbustion chamber, valve means for said air inlet openings and operable in response to pressure variations in the combustion chamber when said plug is moved to a position closing the front end opening of said casing for making the power plant operate as a pulse iet engine, and means actuating said plug to open or close the front end opening in said casing, said means operable to make the power plant operate either as a pulse 'et or a ram jet engine, and an automatically operated control system for said plug actuating means and operable in response to a certain predetermined operation of said power plant.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,142,601 Bleecker Jan. 3, 1939 2,397,357 Kundig Mar. 25, 1946 2,446,266 Cummings Aug. 3, 1948 2,496,351 Mazzoni Feb, 7, 1950 2,514,749 Dobbins July 11, 1950 2,574,460 Bohanon Nov. 13, 1951 FOREIGN PATENTS Number Country Date 596,177 Great Britain July 10, 1947 614,696 Great Britain Dec. 20, 1948 

